#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<arpa/inet.h>
#include<sys/socket.h>
#define BUF_SIZE 30
void error_handling(char *message);
//多播接收端
int main(int argc,char *argv[])
{
	int recv_sock;
	int str_len;
	char buf[BUF_SIZE];
	struct sockaddr_in adr;
	struct ip_mreq join_adr;
	if(argc!=3)
	{
		printf("Usage:%s<GroutIP><PORT>\n",argv[0]);
		exit(1);
	}
	recv_sock=socket(PF_INET,SOCK_DGRAM,0);
	memset(&adr,0,sizeof(adr));
	adr.sin_family=AF_INET;
	adr.sin_addr.s_addr=htonl(INADDR_ANY);
	adr.sin_port=htons(atoi(argv[2]));//多播端口
	if(bind(recv_sock,(struct sockaddr*)&adr,sizeof(adr))==-1)
		error_handling("bind() error");
	join_adr.imr_multiaddr.s_addr=inet_addr(argv[1]);
	join_adr.imr_interface.s_addr=htonl(INADDR_ANY);
	setsockopt(recv_sock,IPPROTO_IP,IP_ADD_MEMBERSHIP,(void*)&join_adr,sizeof(join_adr));
	while(1)
	{
		str_len=recvfrom(recv_sock,buf,BUF_SIZE-1,0,NULL,0);
		if(str_len<0)
			break;
		buf[str_len]=0;
		fputs(buf,stdout);
	}
	close(recv_sock);
	return 0;
}
void error_handling(char *message)
{
	fputs(message,stderr);
	fputc('\n',stderr);
	exit(1);
}
